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If you’ve been diagnosed with hypothyroidism, you should know low thyroid function can impact your gut health. This is why it’s important to properly manage the underlying mechanisms of your hypothyroidism.
An intimate relationship exists between your gastrointestinal tract and your thyroid, with each affecting the other. The health of the stomach, gut microbiome, pancreas, liver, gallbladder, and large intestine are all interrelated with thyroid function.
The most common cause of hypothyroidism today is an underlying autoimmune condition called Hashimoto’s, which attacks and destroys thyroid tissue if left unmanaged. This is important because the inflammation and autoimmune mechanisms associated with Hashimoto’s cause thyroid receptor site resistance and low thyroid function.
Seven ways hypothyroidism affects gut health
1. Intestinal motility
Intestinal motility — the intestinal contractions that move food through the GI tract — is vital to gut health, and it relies on thyroid hormones to function as it should. Many patients with unmanaged hypothyroidism struggle with chronic constipation and depend on magnesium supplements, laxatives, or enemas for regular bowel movements.
The smooth muscles of the GI tract must contract in sequence to move food through, and this movement is called the transit time. The transit time is critical because as soon as you swallow food, it must start moving right away.
If low thyroid activity slows this process, the results are bacterial overgrowth, yeast overgrowth, fermentation of the gut contents, and disruption of the gut microbiome — even if you eat a healthy diet.
2. Gallbladder function
A low functioning thyroid can also cause gallbladder issues, as thyroid hormones significantly impact gallbladder contraction.
When you eat fatty foods, your gallbladder contracts and releases bile into the intestinal tract to emulsify the fats – but low thyroid activity prevents sufficient contraction. As a result, stored bile begins to thicken and create bile sludge, a precursor to gallstones.
If you experience bloating, distention, indigestion, or nausea after eating fatty foods, or if you can’t take fish oils because they cause burping and other intestinal issues, you might want to look into the health of your gallbladder.
3. Leaky gut
A healthy gut requires integrity of the intestinal tight junctions in the gut wall. This prevents intestinal permeability, otherwise known as leaky gut. Gut inflammation and damage lead to leaky gut, which in turn promotes systemic inflammation.
Leaky gut also raises the risk of a condition called endotoxemia, in which end products from gram-negative bacteria make it into the bloodstream and cause systemic inflammation. These byproducts also bind to immune cells in the thyroid gland, causing thyroid inflammation.
4. Oral tolerance
Good oral tolerance means the immune system is not overreacting to the foods you eat and causing sensitivities and inflammation.
Dendritic cells in the gut are immune cells that sample foods that come in and tell the immune system to either react or not react to foods. When people are in a low thyroid state, these dendritic cells tend to overreact to foods and cause an inflammatory reaction.
Good thyroid function helps prevent immune cells in the GI tract from becoming oversensitive, which means you can eat more of the foods you enjoy without worrying about negative reactions.
5. Blood flow to the gut
Healthy circulation delivers nutrients, growth factors, and hormones to the GI tract, keeping the gut functioning and making tissue regeneration possible. It’s important that your gut tissue is regenerating faster than inflammation is causing degeneration.
Blood flow is a key factor in regeneration and dampening inflammation, so when blood flow suffers due to poor thyroid activity, gut health does too.
6. Gut metabolic activity
Another area influenced by thyroid hormones is the body’s metabolism. Metabolic activity supports intestinal motility and the cells in the GI tract depend on good metabolic activity to function and regenerate.
7. Gut microbiome
Studies show the gut microbiomes of Hashimoto’s patients are completely different from those without the disease. This becomes a vicious cycle in which the unhealthy gut microbiome promotes autoimmune diseases, and poor gut function as a result of thyroid hormone deficiency promotes an unhealthy gut microbiome.
Poor gut microbiome health also promotes the loss of oral tolerance and the development of multiple food sensitivities and autoimmune conditions.
Additionally, healthy gut bacteria convert the inactive T4 thyroid hormone to the active T3 form. Your thyroid gland produces hormones 94 percent T4, which must be converted to the T3 throughout the body. Poor microbiome diversity and health make it difficult to produce sufficient T3 to fuel the body’s cells.
To improve your gut microbiome, it’s important to eat a diverse array of vegetables and include plenty of fiber in your diet.
Improving the gut-thyroid connection
How do you get out of this vicious cycle of low thyroid activity and poor gut health?
The first step is to make sure you’re not in a low thyroid state by checking your TSH levels. A healthy range would be between 1.8–3.5.
You should also screen for Hashimoto’s by testing your TGB and TPO antibodies, since it’s important to manage the condition if you have it in order to maintain gut health. You should also take the time to evaluate diet, lifestyle, and environmental factors, all of which contain potential autoimmune triggers.
The bottom line is that a whole-body approach is required to unwind this vicious cycle. It’s not going to happen just by taking a probiotic, a digestive enzyme, or thyroid hormones. Instead, you must treat the underlying autoimmunity and address the autoimmune triggers.
Learn more
I hope this article helped you understand the interrelationship between your gut and thyroid and what you can do to improve the health of both.
This is one of the many concepts I teach in my course, Hashimoto’s: Solving the Puzzle, in which I walk you through the steps of managing your condition and give you questionnaires, recipes, and nutritional strategies.
